Rodionova N A, Dubovaia N V, Eneĭskaia E V, Martinovich L I, Gracheva I M, Bezborodov A M
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia.
Prikl Biokhim Mikrobiol. 2000 Sep-Oct;36(5):535-40.
A method of purification of endo-(1-->4)-beta-xylanase (endoxylanase; EC 3.2.1.8) from the culture liquid of Geotrichum candidum 3C, grown for three days, is described. The enzyme purified 23-fold had a specific activity of 32.6 U per mg protein (yield, 14.4%). Endoxylanase was shown to be homogeneous by SDS-PAGE (molecular weight, 60 to 67 kDa). With carboxymethyl xylan as substrate, the optimum activity (determined viscosimetrically) was recorded at pH 4.0 (pI 3.4). The enzyme retained stability at pH 3.0-4.5 and 30-45 degrees C for 1 h. With xylan from beach wood, the hydrolytic activity of the enzyme (ability to saccharify the substrate) was maximum at 50 degrees C. In 72 h of exposure to 0.2 mg/ml endoxylanase, the extent of saccharification of xylans from birch wood, rye grain, and wheat straw amounted to 10, 12, and 7.7%, respectively. At 0.4 mg/ml, the extent of saccharification of birch wood xylan was as high as 20%. In the case of birch wood xylan, the initial hydrolysis products were xylooligosaccharides with degrees of polymerization in excess of four; the end products were represented by xylobiose, xylotriose, xylose, and acid xylooligosaccharides.
描述了一种从培养三天的白地霉3C培养液中纯化内切-(1→4)-β-木聚糖酶（内切木聚糖酶；EC 3.2.1.8）的方法。纯化了23倍的该酶比活性为每毫克蛋白质32.6 U（产率14.4%）。通过SDS-PAGE显示内切木聚糖酶是均一的（分子量60至67 kDa）。以羧甲基木聚糖为底物，通过粘度测定法确定的最佳活性在pH 4.0（pI 3.4）时记录。该酶在pH 3.0 - 4.5和30 - 45℃下保持1小时的稳定性。对于来自海滩木材的木聚糖，该酶的水解活性（糖化底物的能力）在50℃时最高。在0.2 mg/ml内切木聚糖酶作用72小时后，桦木木聚糖、黑麦谷物木聚糖和小麦秸秆木聚糖的糖化程度分别达到10%、12%和7.7%。在0.4 mg/ml时，桦木木聚糖的糖化程度高达20%。对于桦木木聚糖，最初的水解产物是聚合度超过4的木寡糖；最终产物由木二糖、木三糖、木糖和酸性木寡糖组成。
